The present invention relates generally to electric machines and, in particular, to a stator winding for an electric machine having cascaded end loops. Electric machines, such as alternating current electric generators, or alternators are well known. Prior art alternators typically include a stator assembly and a rotor assembly disposed in an alternator housing. The stator assembly is mounted to the housing and includes a generally cylindrically-shaped stator core having a plurality of slots formed therein. The rotor assembly includes a motor rotor attached to a generally cylindrical shaft that is rotatably mounted in the housing and is coaxial with the stator assembly. The stator assembly includes a plurality of wires wound thereon, forming windings. The stator windings are formed of slot segments that are located in the slots and end loop sections that connect two adjacent slot segments of a conductor of each phase and are formed in a predetermined multi-phase (e.g. three or six) winding pattern in the slots of the stator core. A term phase, utilized herein, is defined as the group of conductors having slot segments disposed in substantially the same core slots. The rotor assembly can be any type of rotor assembly, such as a “claw-pole” rotor assembly, which typically includes opposed poles as part of claw fingers that are positioned around an electrically charged rotor coil. The rotor coil produces a magnetic field in the claw fingers. As a prime mover, such as a steam turbine, a gas turbine, or a drive belt from an automotive internal combustion engine, rotates the rotor assembly, the magnetic field of the rotor assembly passes through the stator windings, inducing an alternating electrical current in the stator windings in a well known manner. The alternating electrical current is then routed from the alternator to a distribution system for consumption by electrical devices or, in the case of an automotive alternator, to a rectifier and then to a charging system for an automobile battery.
One type of device is a high slot fill stator, which is characterized by rectangular shaped conductors that are aligned in one radial row in each slot and that fit closely to the width of the rectangular shaped core slots. High slot fill stators are advantageous because they are efficient and help produce more electrical power per winding than other types of prior art stators. These stators, however, are disadvantageous because the windings are typically interlaced, in which the wires are required to alternate outer and inner radial portions of each slot. This is because one end loop connects the slot segment housed in an outer radial depth of the first slot to a slot segment housed in an inner radial depth of the second slot. This conductor leaves a void in the outer radial depth of the second slot, therefore a second conductor must connect the slot segment housed in an outer radial depth of the second slot to a slot segment housed in an inner radial depth of the third slot. These interlaced windings require an interlacing process to interlace the conductors of all the phases prior to inserting the winding into the core and therefore disadvantageously increase the complexity of placing the winding the stator.
A cascaded winding solves many of the problems associated with the high slot fill stator winding described above. The cascaded winding is described fully in U.S. patent application Ser. No. 10/443,441, filed on May 22, 2003, which is assigned to the assignee of the present application and is hereby incorporated by reference into the present application. The present application is directed to a method of forming the cascaded winding.